Why is the Law of Constant Composition Still Taught?

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SUMMARY

The Law of Constant Composition asserts that a pure chemical compound is always composed of the same elements in a fixed mass ratio. The discussion highlights confusion regarding the term "same elements," using ethanol as an example, which consists of hydrogen, carbon, and oxygen. It emphasizes that while different compounds can share the same elemental composition, they are distinct entities. The participants question the relevance of teaching this law, suggesting it has become trivial and outdated in light of modern molecular understanding.

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It states "a pure chemical compound is always made up of the same elements combined together in the same fixed ratio by mass."
But how can a compound have the same elements ? For example,let's take ethanol,it is composed of hydrogen,carbon and oxygen.So three elements and not the same element.
 
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Dimethyl ether and ethanol are not the same compound, and composed of the same elements in the same ratios. You cannot be picking semantic nits about use of the word "same."
 
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If I were to tell you that my siblings and I have the same parents, would you say that did not make sense because one is a father and the other a mother?

By the way, I don't understand why things like the law of constant composition are still taught. Once we understood what a molecule is, the law became trivial and archaic.
 

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